Si₃N₄matrix ceramics which would be applied to super-high Mach number missile radome was prepared via the reaction sintering process. Si, BN and SiO₂ powder were the main raw materials. The effects of the raw materials and the model processing parameters and the compact density on properties of the material were investigated. The experimental results showed that the material has the best mechanical properties (σ_b, K_ICis 96.7MPa, 1.80MPa.m^1/2, respectively) and better dielectric and thermal physic properties when the content (in raw mixture powder) of Si, BN, SiO₂, is 55%, 30% and 10%, respectively.